1. Field of the Invention
The present invention relates generally to an improved method for remediating contaminated materials. More particularly, the invention pertains to a continuous treatment procedure for the efficient remediation of soils contaminated with hydrocarbons, whereby the treated soils are rendered environmentally safe for use.
2. Description of the Prior Art
Soil contamination caused by the accidental discharge of hydrocarbons is known to have detrimental as well as long-lasting effects on the environment. This type of environmental pollution may result from spillage of fuels into the ground at gasoline service stations from rusted storage tanks or from leakage into earth formations at or near oil wells. Also, spillage of crude oil into the ocean from tankers and offshore facilities can wash ashore to contaminate beaches, shore lines and similar areas. While the problem of hydrocarbon soil contamination remains a continuing one, efforts are underway to cleanup abandoned sites where such contamination has occurred in the past in order to make the areas environmentally suitable for use.
One such cleanup operation involves simply hauling the hydrocarbon contaminated soil to a hazardous landfill site where it can be perpetually isolated from the environment. However, problems with this procedure stem largely from the fact that it is economically expensive and increasingly imposes a limitation on available landfill sites. Moreover, the U.S. Environmental Protection Agency (EPA), charged with the responsibility for implementing and supervising hazardous waste programs, recently promulgated a series of regulations which require that certain wastes containing specified hazardous materials may no longer be deposited in landfills without pretreatment. Government regulations additionally require that soils having a high content of petroleum hydrocarbons, for example, must have environmentally acceptable toxicity levels and exhibit a non-flowing consistency before they can be discarded in a landfill. The end result of these governmental requirements is that hydrocarbon contaminated soils must be subjected to stabilization, detoxification, solidification, or some variation and/or combination thereof, prior to ultimate disposal or reuse.
Various methods for the remediation or treatment of contaminated materials have been proposed in the patent literature. For example, U.S. Pat. No. 4,927,293 to Campbell describes a mechanized remedial method which includes spraying a liquid oxidizing agent, such as hydrogen peroxide, on a mixture containing a calcined absorbent and contaminated material, and then aerating the treated mixture. However, this method is disclosed to result in volatile reaction by-products which must be collected to prevent their release into the atmosphere. Another such procedure includes spraying hydrocarbon contaminated soil with a microbe-containing aqueous solution as set forth in U.S. Pat. No. 5,039,415 to Smith. Again, this prior art procedure releases unacceptable quantities of CO.sub.2 into the atmosphere and is very time-consuming, requiring several days to complete all the steps of the cleanup operation.
U.S. Pat. No. 5,035,537 to Rose discloses a method of treating soil contaminated by hydrocarbon compounds which includes the steps of uniformly dispersing contaminated soil on a surface and applying an emulsifying agent to volatilize the hydrocarbons in the soil. This patent further describes an impervious tent positioned over the treatment area where the volatilized materials are collected and incinerated in order to comply with governmental statues and codes.
U.S. Pat. No. 5,184,917 to Rez teaches a decontamination method wherein petroleum polluted soil is introduced into a cementitious paste to form a shaped concrete mix. The shaped mix is then cured so as to encapsulate the hydrocarbon pollutants in the cured concrete mix and thereby reduce the risk of environmental contamination.
From the foregoing, it is apparent that a need exists for a safe and efficient cleanup method for treating and handling hydrocarbon contaminated soil so that no environmentally unacceptable reaction by-products are released and the treated soil will meet governmental regulations and standards.